Angular sensors can be used in the car industry, for ABS, active suspensions, ASR, dynamic control of the vehicle and ineitial navigation systems; in consumer goods, for image stabilization systems in cinecameras, in sports equipment, in three-dimensional "mice"; in industrial process control, for example in the control of industrial machines, in robotics; in the medical field; and in the military field, for new weapons systems.
Conventional gyroscopes, which are based on conservation of the angular moment of a rotating mass, are too costly and bulky, and are insufficiently reliable for the new applications. In addition, although optical fiber and laser gyroscopes have excellent performance levels, they are too costly for the applications indicated.
The increasing need for small, inexpensive gyroscopes has stimulated development activity in many industrial and academic research centers. In about the 1950s, the first vibrating gyroscopes were thus produced: they measure the angular speed of the systems on which they are fitted, by detecting the effect of the Coriolis force on a mass which vibrates in the non-inertial rotating system. In these sensors it is essential for the sensing mass to be kept moving by means of an actuation mechanism. The first gyroscope produced in the 1950s used a magnetic field for excitation of the sensing mass and detection of the Coriolis force; subsequently in the 1960s, the piezoelectric effect, which is now the most commonly used type, was employed (see for example B. Johnson, "Vibrating Rotation Sensors", Sensors and Actuators, 1995, SAE, SP-1066, pages 41-47).
At present, there is need for vibrating gyroscopes in which the motion-sensing device comprises a silicon microstructure. In fact, the possibility of using machinery and production processes which are typical of the microelectronics industry should make it possible to produce gyroscopes in large volumes and at a low cost, which are essential requirements for car industry and consumer goods applications.